Implement code generation for enums to simplify maintenance

[jpeiffer]

Update the code generation to dynamically read abstract methods with annotations and generate encoders, decoders, and schema files for enums using similar mechanisms to how the json_dynamic_widget package generates code. Also implement a generated schema registration.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.